The present invention relates to a method for manufacturing a tape guide cylinder of small thickness, and particularly relates to a method for manufacturing a tape guide cylinder of small thickness, for example, fitted to an audio or video machine and having the same dimensional accuracy and strength as a conventional tape guide cylinder while being lower in weight and cost than the conventional tape guide cylinders.
A conventional tape guide cylinder for a cassette tape or the like is made of a cut-off pipe processed at both the ends thereof or a wound sheet, or the one made through the impact processing of slag. However, the costs of audio and video machines in general have been required to be reduced, and thus those of the conventional guide cylinders of such kinds have been also required to be reduced. The reduction in the cost of processing and that in the cost of material are only the two ways of reducing the costs of the tape guide cylinders. Introducing an improved press-working process in which forming can be done in a simple manner, or performing an automation to diminish personnel expenses is only the way of reducing the cost of processing of each of the tape guide cylinders. However, since the tape guide cylinders are of the structures as mentioned above, the processing thereof is almost all automated so that the costs of the processing cannot be much reduced even if improved press-working processes are introduced. Besides, since each of the tape guide cylinders is mass-produced in the amount of several hundred thousands to several millions, the cost of processing thereof is already very low apiece. Therefore, decreasing the cost of material as much as possible might be the only practicable way of reducing the costs of the tape guide cylinders. However, since the material for each of the tape guide cylinders is required to be high in surface hardness and non-magnetic, the whole guide cylinders are usually made of a non-magnetic stainless steel of high quality and cost. For that reason, if the material is much used, the cost of the material of each tape guide cylinder cannot be reduced but becomes high. As for the tape guide cylinder made through the impact processing of slag, the tape guide cylinder is made of aluminum or brass and has its outside surface subjected to hard chromium plating.
Thus, decreasing of the thickness of material sheet for each of the conventional tape guide cylinders is attempted so as to reduce the cost of material therefor. However, since the reference inside and outside diameters of each tape guide cylinder are standardized for the forming of a cassette, the thickness of the material sheet can hardly be decreased. In other words, if the inside diameter of the tape guide cylinder is fixed to the standardized value and the thickness thereof is diminished, the outside diameter thereof decreases to make it likely that the cassette tape is located closer to the body of the cassette to come into contact therewith and be scratched. On the other hand, if the outside diameter of the tape guide cylinder is fixed to the standardized value and the thickness thereof is diminished, the inside diameter thereof becomes larger than the standardized value to allow the tape guide cylinder to play not to function properly when fitted on guide cylinder attaching shafts. In that case, the design of the cassette needs to be changed, and thus result in the increase in the costs of producing the cassettes. Nevertheless, the manufacturers of such tape guide cylinders have been striving to reduce the costs thereof to win an international competition, but have not succeeded in much reducing the costs thereof.